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NVD / CVE Program· CNA canonical

CVE-2021-3490: Linux kernel eBPF bitwise ops ALU32 bounds tracking

Noroxi assessment

Priority: Plan (action score 40/100)

  • A ready-made attack module is public (Metasploit); exploiting it takes no special expertise.
  • Because a ready-made attack tool exists, priority is at least “Plan”.
  • Probability of exploitation in the next 30 days: 27.3% (FIRST EPSS); higher than 98% of all records.
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: linux (Debian:12) 5.10.38-1; kernel-livepatch-SLE15-SP3_Update_0 (SUSE:Linux Enterprise Live Patching 15 SP3) 2-3.1.

Add it to your regular patch cycle. Upgrade to linux (Debian:12) 5.10.38-1; kernel-livepatch-SLE15-SP3_Update_0 (SUSE:Linux Enterprise Live Patching 15 SP3) 2-3.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

HighCVSS 7.8 · v3.1—Weaponized Fix available
Published
Jun 3, 2021
Updated
Jun 17, 2026
EPSS
27.3% · 98th percentile

Report tools

JSON

Action score

40

Plan

Add it to your regular patch cycle.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
8 / 30 · 27.3%
Ready-made attack tool
1 / 40 · floor: at least 40

CNA vs NVD score

NVD
7.8
CNA · canonical
7.8
agree

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Weaponized exploit exists
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel
canonicalubuntu linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • canonical ubuntu linux20.04
  • canonical ubuntu linux20.10
  • canonical ubuntu linux21.04
  • linux linux kernel5.11 and later · before 5.11.21
  • linux linux kernel5.12 and later · before 5.12.4
  • linux linux kernel5.10 and later · before 5.10.37
  • linux linux kernel5.13

Versions reported by the vendor

Affected version ranges reported by the assigning authority (canonical). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux kernel

    • trunk and later · before v5.13-rc4affected
    • linux-5.12.y and later · before v5.12.4affected
    • linux-5.11.y and later · before v5.11.21affected
    • linux-5.10.y and later · before v5.10.37affected
    • v5.7-rc1 and later · before 5.7*affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.10.38-15.10.38-1
SUSE:Linux Enterprise Live Patching 15 SP3kernel-livepatch-SLE15-SP3_Update_0before 2-3.12-3.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2020-10742Jun 2, 2021 · A flaw was found in the Linux kernel.
    24Monitor
  • ← EarlierCVE-2021-3489Jun 3, 2021 · Linux kernel eBPF RINGBUF map oversized allocation
    31Monitor
  • Later →CVE-2021-3491Jun 3, 2021 · Linux kernel io_uring PROVIDE_BUFFERS MAX_RW_COUNT bypass
    35Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:linux5.10.38-1 · Debian:12Package registry (OSV)
suse:kernel-livepatch-SLE15-SP3_Update_02-3.1 · SUSE:Linux Enterprise Live Patching 15 SP3Package registry (OSV)

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Metasploit module ×1
  • Proof-of-concept repository on GitHub ×5

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Metasploit moduleexploit/linux/local/cve_2021_3490_ebpf_alu32_bounds_check_lpeLinux eBPF ALU32 32-bit Invalid Bounds Tracking LPEexploit2021-05-11
Proof-of-concept repository on GitHubstars:3172021-06-24
Proof-of-concept repository on GitHubstars:22023-04-06
Proof-of-concept repository on GitHubstars:02026-03-03
Proof-of-concept repository on GitHubstars:02026-03-04
Proof-of-concept repository on GitHubstars:02026-07-21

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Metasploit-24 d
  2. Published
  3. First PoC+20 d
  4. TodayNov 4, 2026+1980 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

—

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

  • CVE-2002-243816 days apartTCP firewalls could be circumvented by sending a SYN Packets with other flags (like e.g.
    31Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-20 · Improper Input Validation

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records